The back-thinning of wafers is often necessary in the semiconductor industry and can take place mechanically and/or chemically. For purposes of back-thinning, in general the wafers are temporarily fixed on a carrier, there being various methods for the fixing. As carrier material, for example, films, glass substrates or silicon wafers can be used.
Depending on the carrier materials used and the interconnect layer used between the carrier and the wafer, different methods for dissolving or destroying the interconnect layer are known, such as, for example, the use of UV-light, laser beams, temperature action or solvents.
Stripping increasingly constitutes one of the most critical process steps since thin substrates with substrate thicknesses of a few μm easily break during stripping/peeling or are damaged by the forces that are necessary for the stripping process.
Moreover, thin substrates have hardly any stability of shape or none at all and typically curl without support material. During handling of the back-thinned wafer, therefore, fixing and support of the wafer are essentially indispensable.
DE 10 2006 032 488 B4 describes a method for heating the bonding substance by means of laser light, the connecting action of the bonding substance being neutralized by the associated considerable temperature increase to 400 to 500° C. Thus, the problem of heating the entire wafer stack (see there: [0021]) is solved. At least the edge region and—due to good thermal conductivity of the wafer material—also the region adjacent to the edge region are, however, subjected to a considerable temperature increase. The problem here is also the resulting temperature gradient.